Detonation-wave shaper



D. l.. coURsEN 3,035,518

DETONATION-WAVE SHAPER May 22, 1.962

Filed May 25, 1959 4 Sheets-Sheet 1 May 22, 1962 D. l.. coURsENDETONATIoN-wAvE SHAPER 4 Sheets-Sheet 2 Filed May 25, 1959 zFl'g. 5

INVENTOR. DAVID L. COU RSEN gmkb( @Lny May 22, 1962 D. L.. couRsENDEToNATIoN-WAVE SHAPER 4 Sheets-Sheet 3 Filed May 25 1959 INVENTOR.DAVID L. COURSEN @mm/img May 22, 1962 D; couRsEN 3,035,518

DEToNATIoN-WAVE SHAPER Filed May 25, 1959 4sheets-sheet 4 INVENTOR.DAVID L. COURSEN Byggmmmy 3,035,5l8 Patented May 22, 1962 tice 3,035,518DETONATN-WA\E SHAPER David L. Coursen, Newark, Del., assignor to E. I.du Pont de Nemours and Company, Wilmington, Del., a corporation ofDelaware Filed May 25, 1959, Ser. No. 815,336 8 Claims. (Cl. MBZ-22) Thepresent invention relates to a novel high-explosive device wherein thenatural detonation front is distorted. More particularly, the presentinvention relates to a highexplosive device wherein a detonation frontgenerated at one locus is made VtoY arriveV simultaneously at a plu-Vrality of loci along a desired boundary. This application is acontinuation-in-part of my co-pending application Serial No. 739,529,now abandoned, tiled June 3, 1958.

When a mass of a high explosive is initiated at one locus, the resultantdetonation wave proceeds outwardly from the locus at uniform velocity inall directions. For example, when a thin, iiat circular charge of a highexplosive is initiated at the center, the detonation front proceedsthrough the charge in the form of an expanding circle and arrivessimultaneously at all points along the perimeter of the charge. When thethin, flat charge has straight line boundaries, the detonation frontinitially constitutes an expanding circle until the portion of theboundary nearest the point of initiation is reached, thereafter thefront travels through the remainder of the charge as an expanding arcof'a circle, the radius of curvature of the arc at any given point inthe charge being determined by the distance from the initiation point,lt is obvious that in the latter case, the detonation front, because ofits curvature, does not arrive simultaneously at all points along theperiphery of the charge but arrives at various times, depending upon thedistance between each nish locus and the starting, or initiation, locus.Obvious also is the fact that the detonation front cannot arrivesimultaneously at a number of loci along a curved line which does notcoincide 'with the natural curvature of the detonation front.

In many industrial applications of explosives aside from blasting,improved results are obtainable when the explosive charge is initiatedsimultaneously at a plurality of loci along its surface, For example,when a linear, or wedge-like, shaped charge, such as that described inU.S. -Patent 2,605,704 (Jacques Dumas, August 5, 1952) for slotting pipeand the like, is initiated at a plurality of loci in a straight linealong its surface, rather than at one locus, increased uniformity ofpenetration is obtained. Also, in the method of joining metal elementsexplosively as described in U.S. Patent 2,367,206 (C. O. Davis, to duPont, January 16, 1945), localized initiation of the explosive chargesurrounding the metal sleeve in the assembly sometimes results in damageto the juncture, whereas such damage does not occur when the sleeve-likecharge is initiated at a plurality of loci delining a circle around oneend of the charge.

The use of a series of individual initiators, such as blasting caps, toeifect the simultaneous initiation at a number of loci along a straightor curved line is not always feasible, because the eccentricities of theindividual initiators, although slight enough to -be generally ignored,preclude the accomplishing of the desired truly simultaneous initiation.Moreover, the mechanical assembly of a large number of the initiatorsadjacent to the surface of the high explosive to be initiated isextremely diiiicult, if not impossible, due to space requirements. Thebrisance, or shattering action, of the individual initiator also mayprohibit the use of such a large number of the initiator-s in closeproximity because of their destructive effects. The provision of a linewave generator, i.e. a device wherein a detonation front generated atone locus is distorted so that it arrives simultaneously at a number ofloci along a straight or curved line, is of great value in the art.

One type of such a line wave generator has been provided and comprises aflexible sheath containing a number of inert spacing members which forma network of interstices in which is disposed a high explosive. When thedetonation propagates along all the various equilength paths dened bythe spacers, the front arrives simultaneously at all the finish locidelineating the desired line. This device, which is described in U.S.Patent 2,774,306 (N. A. MacLeod, December 18, 1956), however, not onlysufers from the complexity of design, the number of components in thedevice resulting in complications of fabrication, but also at timesgives unsatisfactory results. The detonation front naturally can by-passone or more of the right-angle turns of the equilength explosive pathsand can out corners, following a shorter route. Since 4the explosiveconstituting the line wave generator detonates at constant velocity, thetime required to travel a longer route exceeds that required for travelalong a shorter route. Thus, the detonation front, instead of arrivingat all the nish loci simultaneously, arrives at different times, thosesegments of the front which cut corners arriving before those making theright-angle turns.

Accordingly, an object of the present invention is the provision of anexplosive device wherein the detonation front generated at a singlelocus is made to arrive simultaneously at a plurality of loci along acurved line or one or more straight lines. Another object of the presentinvention is the provision of an explosive device suitable for use as asimple and efficient line wave generator. A further object of thepresent invention is the provision of an explosive device which isfacilely and inexpensively manufactured. A still further object of thepresent invention is the provision of an explosive device whereby theinitiation of an adjacent explosive charge at a plurality of loci alongits surface can be induced simultaneously in an etiicient manner. Otherobjects will become apparent as the invention is further de-` scribed.

The foregoing objects may be achieved when I provide a line wavegenerator comprising a barrier plate, a lrst set of explosive trains onone side of the barrier plate, and a second set of explosive trainsnon-parallel to the tirst set on the opposite side of the barrier plate,each of the explosive trains being of a cap-sensitive high explosive ofsuicient cross-sectional area to support detonation and spaced yfrom anytra-in in the same set by a distance equal to at least twice thethickness of the barrier plate, the barrier plate having a thicknesssuch that propagation of the detonation from a train in one set to atrain directly opposite in the other set is delayed for an interval 0ftime substantially equal to the time required for the detonation totraverse the width of a train, the two sets of trains togetherconstituting detonation paths from a single initiation locus to aplurality of finish loci delineat- -ing a predetermined line, theshortest paths from the initiation locus to any of the finish loci beingequal in length.

Throughout this description, the terms locus and loci have been used todesignate that portion of an explosive train at which detonation isinitiated or to which detonation is propagated. inasmuch as theexplosive train must be three-dimensional, the use of the terms locusand loci is believed more appropriate than would be the terms poin f andpoints However, for a mathematical treatment of the devices of thepresent invention, the consideration of the loci as points isappropriate.

lIn order to describe more `fully the nature of the present invention,reference is made to the accompanying gures.

FIGURE 1 is an illustration of the phenomenon of corner cutting Iinintersecting explosive trains.

FIGURES 2A and 2B are illustrations in top and end views, respectively,of the relationship of the explosive trains in the present invention,whereby the undesirable eiect of corner cutting is overcome.

FIGURE 3 represents a top view greatly enlarged of one embodiment of thepresent invention which embodiment is constructed in accordance with theprinciples illustrated in yFIGURES 2A and 2B.

FIGURE 4 is a cross-sectional end view taken on line 4--4 of FIGURE 3.

-FIGURE 5 represents a top view greatly enlarged of another embodimentof the present invention, which embodiment again is constructed inaccordance with the principles illustrated in FIGURES 2A and 2B.

FIGURE 6 shows in top view and enlarged form Ystill another embodimentof the present invention; this embodiment also is constructed inaccordance with the principles illustrated in FIGURES 2A and 2B. FIGURE6 is greatly simplified, only a 'few of the explosive trains being shown`fer the sake of clarity.

FIGURE 7 shows in top view the embodiment of FIG- URE 6, FIGURE 7 beingso drawn as to illustrate a particular characteristic of this embodimentof the present invention.

Referring now to the iigures in more detail, FIGURE l shows intersectingexplosive trains 8 and 9, and the position of a detonation front isshown at successive equal time intervals by lines 1, 2, 3, 4, 5, 6, and7 drawn across trains 8 and 9. Lines 1a, 2a, and 3a indicate thediverging shock fronts corresponding to the detonation fronts at l, 2,and 3, respectively. A similar shock -front exists corresponding to eachdetonation front but these shock fronts are omitted for the sake ofclarity. The detonation front at 3 in train `8 initiates loci 10 whichserve as focal loci for the propagation of detonation in train 9.Because train y9 is not initiated -at the midpoint of the intersectionof trains 8 and 9, but is initiated instead at loci 10, i.e., thedetonation cuts corners instead of making a right angle turn at themidpoint of the intersection, the detonation fronts at time intervals 4,5, 6, and 7 in train 9 are farther from the midpoint of the intersectionthan is the detonation front in train 8 at the same time intervals.

FIGURES 2A and 2B show explosive train 18 crossing over but notintersecting explosive train 19. The space between trains 18 and 19 maybe occupied by a barrier plate (not shown) which will be describedlater. Again, the position of a detonation front is shown at successiveequal time intervals by lines 1, 2, 3, 4, 5, 6, and 7 drawn acrosstrains 18 and 19. Lines 1a, 2a, 3a, and V4a indicate the diverging shockfronts generated by detonation fronts at 1, 2, 3, and 4, respectively.Because trains 18 and 19 are separated, neither the detonation front at3 nor the shock front at 3a can initiate train 19. However, when thedetonation front in train 18 reaches position 4, corresponding shockwave 4a initiates train 19 at loci 10. Thus, the detonation fronts attime intervals 5, 6, and 7 in train 19 are the same distance as is thedetonation front in train 18 at the same time intervals from themidpoint of the overlapping portions of trains 18 and 19. The separationof trains 18 and 19 thereby overcomes the undesirable effect of cornercutting. The end result of introducing a space between explosive trains1S and 19 is the same as though the detonation progressing through train18 made a right-angle turn into train 1'9 at the midpoint of theoverlapping portions of trains 18 and 19.

FIGURE 3 illustrates a storm of the present line wave generator designedso that the detonation front generated at locus P0 arrivessimultaneously at nish loci P1v to Pn to give a straight-line front.This embodiment comprises a set of parallel explosive trains Emaintained within the grooves of a supporting plate (not shown) on thetop of barrier plate B and a second set of parallel explosive trains Emaintained within the grooves of a supporting plate on the bottom ofbarrier plate B. Trains E are diagonally disposed with respect to trainsE' to lform a triangular grid wherein trains E traverse, i.e., crossover but do not intersect, trains E.

Upon initiation at locus P0, the detonation can follow a number ofpossible paths, some of which are indicated on FIGURE 3 by dotted lines.For example, the detonation can propagate Without deviation along anyone explosive train in either set of trains. This action is illustratedby the straight dotted line between initiation locus P0 and iinish locusP1. Alternatively, the detonation can cross back and forth between the Eand E explosive trainsat the places at which the trains traverse. Thisaction is illustrated by the zig-zag dotted lines on the drawing, onezig-zag line indicating a detonation which branched off the P11-P1 pathto arrive at finish locus P10, and the other dotted line indicating adetonation which branched oii. the P11-P10 path to arrive at inish locusP12.

If explosive trains E and E in-tersected each other,

detonations along paths P11-P10 and P11-P12 could cut corners asillustrated in FIGURE l, thus causing the resultant detonation front tobulge, eg., the detonation front would reach loci P10 and P12 prior toreaching loci P1 Iand Pn. This bulging of the front is the situationwhich occurs in the afore-mentioned patented line wave generator.However, when, as in accordance with the present invention, a barrierplate is interposed between the two sets of explosive trains, the delayoccasioned by passage of the detonation through the barrier prior toinitiation of detonation in the oppo-site'train can be made tocompensate for the time saved by cutting corners. Obviously, then, byequalizing the time required for the detonation to travel all theinitiation locus-to-nish locus paths regardless of their length ortortuosity, the detonaftion which propagates at constant velocity can bemade to arrive simultaneously at all the iinish loci. In the embodimentshown in FIGURE 3, the detonation front delineates a straight line atany given distance beyond the traverse loci nearest the initiation locusP0.

FIGURE 4 shows explo-sive trains E maintained within the grooves ofsupport plate S on the top of barrier B, and similarly, explosive trainsE maintained within the .grooves of support pla-te S' on the bottom ofbarrier B.

FIGURE 5 illustrates a line' Wave generator so designed that thedetonation front generated at Ia central initiation locus P0 arrivessimultaneously at a plurality of nish loci, some of which are indicatedby P1 to P3, delineating a square. The explosive trains and barrier areagain indicated by E and E and B. This generator actually comprises 4 ofthe triangular grids of FIGURE 3, `abutted to give a square rectilineargrid. Thus, the action of this grid and its construction principlesessentially are identical to those of the FIGURE 3 embodiment.

In FIGURE 6, E, E', B, and P0 again identify the explosive trains,barrier, and initiation locus, respectively. In this embodiment of theinvention shown in simplified `for-m, the explosive trains in both setsare spirals, the parallel sets being superimposed so that the spirals ofset E are oppositely directed to those of set E. In this contiguration,the detonation travels las in the FIGURE 3 embodiment, but thedetonation initiated at P0 converges and finally arrives simultaneouslyat a Series of iinish loci defining circle C, the original curvature ofthe front as generated being invented.

FIGURE 7 illustrates the eiect of multipoint initiation of theembodiment of FIGURE y6, E, E', B, P0, and C being as in FIGURE 6. Forconvenience of illustraltion, 'the trains, shown as separated by atransparent barrier, are indicated by lines. When point sourceinitiation is used, the converging detonation front will achievecircular for-m at the series of nish loci delineating circle C; thefront prior to arrival at these loci delineates an arc di I' a of thecircle. If, however, the detonation is initiated at two loci, P and Po',on the grid periphery, the front will delineate -a complete circle at aseries of loci nearer the periphery of the charge, to give a circle oflarger circumference, C. Initiation at locil P0, P0', and P0 will give acircle of even larger circumference, C". As is evident, for a given linewave generator constructed in accordance with this embodiment of theinvention, the circumference of the circle defined bythe nish locus maybe regulated to some extent by the number of initiation loci used.

The following examples `are presented to illustrate specific embodimentsof the present invention. However, they will be understood to beillustrative only and not as limiting the invention in any manner.

Example 1 A square 6 x 6 inch brass plate was engraved 'with a series ofdiagonal, parallel, equidistant grooves. Upon this die was placed a 6 X6 inch square 0.005 inch-thick lead foil and then the matching punch waspressed down on the foil and die. Onto the resultant grooved foil waspoured a water slurry of nely divied PETN containing 1% gum arabic as aiiow promoter. The raised portion of the foil was wipe-d clear of theslurry, and the water was allowed Ito evaporate from the grooves,leaving PETN trains of 0.8-square millimeter cross-sectional area in thegrooves. Another PETN-containing lead foil was prepared in similarmanner. The two foils were fastened together in face-to-face arrangementby a 6 x 46 inch sheet of pressure-sensitive adhesive tape, the adhesivemix being presen-t on both sides of the sheet. The thickness of thesheet, i.e. the barrier, was 8 mils. Upon central initiation of theresultant rectilinear grid (FIGURE 3) by `an electric blasting cap, thedetonation wave thus generated was distorted to arrive simultaneously ata plurality of finish loci on the periphery of the grid.

Example 2 The procedure of Example 1 was repeated with the exceptionthat l8-mil-thick tape barrier was replaced by a barrier comprising 4layer-s of the tape and one layer of 9-mi1-thick polyethylene sheeting,the polyethylene being sandwiched between double layers of the tape. Theresultant barrier had `a thickness of 41 mils. Satisfactory results wereobtained upon testing this square grid, which upon diagonal cutting ofcourse would give 4 of the triangular grids of FIGURE 3.

Example 3 A series of square grids having various barriers were preparedaccording to the procedure of Example 1 and were tested successfully.The lbarrier construction is given in the following table.

Two circular sheets of lead foil were impressed by means of matched dies`with a set of spiral grooves. The grooves were filled with linelydivided PETN by the procedure of Example 1, the cross-sectional area ofthe resultant explosive trains being 0.5 square millimeter.

The explosive-containing surface of each foil was covered with acircular sheet of the 8milthick double-coated adhesive tape, and a layerof 49-mil-thick cardboard was fastened between the parallel foils whichwere in face-toface relationship so that the spirals of one foil wereoppositely directly to those of the other foil. When the resultantcircular grid (FIGURE 7) was initiated at one locus on its periphery,the detonation front eventually assumed circular shape near the centerof the grid. A similar grid initiated at two opposite loci on theperiphery gave a circular detonation front of larger circumference.

Although the grid-type line wave generators of the present invention maybe prepared readily by the afore-described procedure using supportplates, i.e. the lead foils, the units may also be prepared withoutsupport plates by use of the followingprocedure.

Example 5 Onto a triangular sheet of cardboard the surfaces of which arecovered with adhesive are extruded a number of diagonal, parallel stripsof an RDX-containing extrudable composition. After setting up of thecomposition, a number of explosive strips are extruded on the oppositesurface of the cardboard barrier such that their direction is oppositeto that of the previously extruded strips, i.e. the strips of onesurface are non-parallel to those of the ther surface.

The action of assemblies constructed as described in Examples l, 2, 3,and 4 was determined by high speed X-ray photography. As the trainsdetonate, the lead foil directly over the trains is disintegrated andthus no longer forms a barrier for X-rays. Thus, the photographsobtained had light-colored sections representing the undamaged lead foiland darkened sections indicating the portions disintegrated by thedetonation. In all cases, the photographs clearly showed the detonationfront proceeding in a line corresponding to the design of the assembly.

As has been illustrated, the desired distortion of the detonation -frontmay be achieved readily in a number of ways without excessivecomplications of fabrication. The only critical features required toachieve the distortion are: (l) that the explosive trains constituting aset must be nonconnected to each other and must be nonparallel to thetrains of the other set, (2) that the planes of two sets must beparallel, (3) that the high-explosive trains must be of sufficientcross-sectional area to support the detonation, and (4) that the barrierplate separating the two parallel sets must be of such thickness as todelay for `a short interval of time the propagation of the detonationfrom a train in one of the sets to the opposite train in the other set.The first two features of course are inherent to the structure of agrid, but in the present explosive grid, in contrast to conventionalgrids, any given train in one set does not actually intersect buttraverses, i.e. crosses without contact, a train in the other set. Uponthe basis of the afore-listed four considerations, many variations ofthe line wave generators, in addition to the exemplified variations, maybe prepared to produce linear detonation fronts of various geometricforms.

The exact explosive composition used is not critical so long as theexplosive material detonates in the grid at high velocity, e.g. at least3000 meters per second, and is cap sensitive. Such cap-sensitive highexplosive materials include PETN, RDX, HMX(cyclotetramethylenetetranitramine), tetryl, lead azide, andnitroglycerin among others. Although the exact cap-sensitivehigh-velocity material used is a matter of choice based upon suchconsiderations as economics, availability, and the like, PETN because ofits general availability and ease of handling is preferred. The specificexplosive used also will depend somewhat upon the method of fabricationused in preparing the explosive grid. In the extrusion processexemplied, naturally an extrudable composition, such as that of Example5 or one of the conventional nitroglycerin-based compositions or thelike, would be used. Greater adaptability with respect to explosivecomposition is possible of course in other fabrication methods, e.g. thesupport plate method.

As indicated, the exact method used to prepare the grids does not form apart of the present invention but rather is in the purview of themechanical arts. Use of the support plates does to some extent simplifyoperations. However, the plates themselves do not constitute anessential feature of the explosive grid. Naturally, the confinementoffered by such support plates as lead foils does influence thedetonation inasmuch as confinement increases the detonation velocity.For this reason, the use of these plates may be desirable at times, forexample when increase in the detonation velocity of a given explosivemay be desired or necessary. Although lead foil plates were used in theexamples to permit X-ray photography of the grid detonations, thematerial of the support plates is not critical, any material beingsuitable which is of a nature such that it can be formed into a supportmedium `for noncohesive, e.g. free-flowing, explosive compositions. Forexample, grooves could also be formed in a thermoplastic syntheticmaterial such as polyethylene by a hot-pressing operation.

The minimum cross-sectional area of the explosive train necessary forsupport of the detonation is dependent upon the specific explosivecomprising the trains, since the minimum detonation-supporting area is adirect function of the explosive. I have determined that for a verysensitive explosive, this minimum area is 0.09 square millimeter.However, as stated previously, the specific value of the cross-sectionalarea will vary with the specific explosive used, the exact minimumcross-sectional area not being a fixed value.

The trains of explosive Within a set are spaced apart a distance equalto at least twice the thickness of the barrier plate to insure that thedetonation can propagate more rapidly through the barrier than from onetrain to an adjacent train in the same set. The maximum distance betweenthe explosive trains in a set is not critical, but is, of course,governed by the number of loci desired along the finish line.

A large number of materials are suitable for use as the barrier plate,including paper, e.g. cardboard, a plastic film such as polyethylene,polyvinyl chloride, et cetera, cloth, felt, cork, and the like.Adhesives used to fasten the assembly together also act as a portion ofthe barrier plate, and, as exemplified, such integral combinations of anadhesive and other materials as the pressure-sensitive adhesive tape`function satisfactorily.

The thickness of the barrier plate required to delay for a shortinterval the propagation of the detonation from one explosive train toits opposite train is a function of the variable conditions: barriermaterial, specific explosive used, and cross-sectional area of theexplosive train. I have found that the least thickness of barrier plate,regardless of the above listed conditions, required to delay suchpropagation is 4 mils. Thus, the minimum lower limit on barrierthickness may be set at 4 mils, the exact minimal thickness not being aspecific value but being governed and determined -by the aforo-mentionedvariables. Obviously, the barrier plate must be of such dimen sionsmerely to delay the detonation propagation and not to prevent entirelysuch propagation.

Furthermore, the over-all dimensions of the grid, i.e. its llength andwidth or its circumference, are not critical. On a practical basis,these dimensions will be limited by economics, that is, the use of agrid which is beyond the size necessary to effect the desired distortionis unfeasible, because unnecessary increases in size increase to nopurpose the amount of explosive material and the like required for itsconstruction.

As indicated by references to the relationship of the -triangular gridof FIGURE 3 and the square grid -of FG-` URE 5, the final configurationof the detonation front l may bevaried by using a section of a grid, forexample a triangular portion of the square grid to obtain a straightline rather than a square detonation front or half of the spiral grid toobtain a semicircular detonation front. A number of the explosive gridsmay be disposed over a surface to provide simultaneous initiation atmany points on the surface. For example, a spherical explosive chargemay be symmetrically surface-initiated by disposing a number of gridsproviding semicircular detonation fronts about the sphere in such mannerthat the grids form longitudinal fins about the sphere. Theselongitudinal fins meet at the poles of the sphere, thus `providing anaxis common to all of the grids. Initiation of the grids at either endor simultaneous initiation at both ends of the axis thus lformed willprovide simultaneous initiation at many points on the surface of thesphere.

The invention has been described in detail in the foregoing. However, itwill be apparent to those skilled in the art that many variations, forexample in the specific explosive used and in the configuration anddimensions of the grid, are possible without departure from the scope ofthe invention. I intend, therefore, to be limited only by the followingclaims.

I claim:

1. A line-wave generator which provides a detonation front along apredetermined line comprising a plate, a rst set of explosive trains inlateral array on one side of and contiguous to said plate, and `a secondset of explosive trains in lateral array on the opposite side of andcontiguous yto said plate, the first set of trains lying in a planeparallel to the plane of said second set of trains While the individualtrains of said first set are non-parallel to and cross without contactthecomparable individual trains of said second set, Ithe `trains in eachof said sets being of a cap-sensitive high explosive of sufficientcross-sectional area to support detonation and spaced apart from anytrain in the same set by a distance equal to at least twice thethickness of said plate, all of said trains having substantially uniformand equal cross-sectional area, said plate having an essentially uniformthickness such that propagation of the detonation from the train in oneof said sets to a train directly opposite in the other set is delayedfor an interval of time substantially equal to the time required for thedetonation to traverse the width of a train, said first and second setsof trains together constituting means for conveying the detonation froman initiation locus to each of a plurality of finish loci delineatingsaid predetermined line, the shortest path from said initiation locus toany of said finish loci being equal in length to that of the shortestpath to any other of said finish loci.

2. A line-wave generator which provides a detonation front along apredetermined line comprising a plate, a rst set of explosive trains inlateral array on one side of and contiguous to v said plate, and asecond set of explosive,

trains in lateral array on the opposite side of and contiguous to saidplate, the rst set of trains lying in a plane parallel to the plane ofsaid second set of trains while the individual trains of said first setare non-parallel to and cross without contact the comparable individualtrains of said second set, the trains in each of said sets being of acap-sensitive high explosive of at least 0.09 square millimeter incross-sectional area in order to support a detonation and spaced fromany train in the same set by a distance equal -to at least twice thethickness of said plate, al1 of said trains having a substantiallyuniform and equal cross-sectional area, said plate having an essentiallyuniform thickness of at least about 4 mils such that propagation of'thedetonation from a train in one of' said sets 'to a train directlyopposite in the other set is delayed for an interval of timesubstantially equal to the time required for Ithe detonation to traversethe Width of a train, said first and second sets of trains togetherconstituting means for conveying a detonation from an initial locus toeach of a plurality of finish loci delineating said predetermined line,the shortest path from said initiation locus to any of said finish locibeing equal in length to that of the shortest path to any other of saidinish loci.

3. A line-wave generator according to claim 2 wherein the individualexplosive trains within each separate set of trains are all parallel toeach other. l

4. A line wave generator according to claim 2, wherein the explosivetrains of each of said sets are spirals.

5. A line wave generator according to claim 2, wherein saidcap-sensitive high explosive is PETN.

6. A line wave generator according to claim 2, wherein said barrierplate is selected yfrom the group consisting of paper and plastic ilm.

7. A line wave generator according to claim 2, wherein the explosivetrains of each of said sets are maintained within a supporting plate.

8. A line wave generator according to claim 7, wherein said supportingplate is of lead.

References Cited in the le of this patent UNITED STATES PATENTS

